Robert Ford spent the rest of his life trying to capitalize on the fame of being the man who killed Jesse James. It's hard not to suspect that a twisted thought of the same kind must have been behind the murder of Chris Kyle, the sniper credited with the most kills in US history. It also brings to mind the standard Western plot in which a young, unknown challenger brings down a famous gunslinger, only to find that his new fame has made him the target of all the other ambitious young punks.
This, no doubt, is a part of what Jesus meant when He said, "All that take the sword shall perish with the sword." It is, after all, simply a statement of fact which is supported by experience, although exceptions certainly abound. After all, it is no coincidence that Yamamoto, George Custer, and Stonewall Jackson were all killed in military actions; they were military men, and, from a purely secular viewpoint, the odds will catch up with you one day.
Since many obviously have trouble reading the words in front of them, it's also worth pointing out that Jesus did not use the subjunctive mood. He did not say, "All that take the sword should perish with the sword;" He did not say that this was something they deserved or had coming, nor that they were innocent and pure as the driven snow. He merely said that this is something that would happen -- much as if He had said, "All that keep bees shall be stung by bees."
Well, some of us have to keep bees, or none of us would have honey, to say nothing of the crops pollinated by domesticated bees. Some likewise have to take the sword: "For he is God's minister to thee, for good. But if thou do that which is evil, fear: for he beareth not the sword in vain. For he is God's minister: an avenger to execute wrath upon him that doth evil." In the case of St. Peter, though, it was God's will that he live by the cross and die by the cross -- quite literally, since he was crucified upside down.
All this shows that the background to Ron Paul's recent tweet was not quite as simplistic as many make it out to be. It is of course possible that Ron Paul's understanding was equally simplistic, and one way or the other it was an unnecessary and ill-timed remark. It's startling, though, that so many are willing to ignore Christ in an attempt to honor Chris.